| 摘要 |
An optical fiber is constituted by: a three-layer structured core which includes, a first core (having a relative refractive index difference of &Dgr;1 in a region of a radius of R1), a second core (having a relative refractive index difference of &Dgr;2 in a region from the radius R1 to a radius of R2), and a third core (having a relative refractive index difference of &Dgr;3 in a region from the radius of R2 to a radius of R3), wherein the relative refractive index differences have relationships of &Dgr;1>&Dgr;2, &Dgr;3>&Dgr;2, and &Dgr;3>&Dgr;1, when &Dgr;1−&Dgr;2=X and &Dgr;3−&Dgr;2=Y, (X+Y)>0.4% is satisfied, and X and Y satisfy 0.25%<X<0.6%, 0.1%≦̸Y≦̸0.6%, and a relationship of (2*X−0.7)%<Y<(X/2+0.4)%, thereby satisfying the G652 standard and having an SBS threshold equal to or higher than that of an optical fiber having the same MFD by +3 dB or higher.
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